Encapsulation compositions

ABSTRACT

Carbohydrate-based glassy matrices which are stable in the glassy state at ambient temperatures may be prepared by the use of aqueous plasticizers with melt extrusion. Such glassy matrices are useful for the encapsulation of encapsulates, in particular, flavoring agents.

This is a Division of application Ser. No. 08/424,572 filed on Apr. 17,1995, now U.S. Pat. No. 5,603,971, which is a Continuation ofapplication Ser. No. 08/098,885, filed Jul. 29, 1993, abandoned, whichis a Continuation-in-part of application Ser. No. 08/047,196, filed Apr.16, 1993, abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to encapsulation compositions in which anencapsulate is encapsulated in a glassy matrix. More particularly, thepresent invention relates to flavor encapsulation compositions in whicha flavoring agent is encapsulated in a glassy matrix.

2. Discussion of the Background

The encapsulation of encapsulates is an area of active research. Inparticular, the encapsulation of encapsulates such as medications,pesticides (including insecticides, nematocides, herbicides, fungicides,microbicides, etc.), preservatives, vitamins, and flavoring agents isdesired for a number of reasons. In the case of medications andpesticides, such encapsulation may be desired to achieve the controlledrelease of the medication or pesticide. In the case of vitamins, theencapsulation may be carried out to protect the vitamin fromair-oxidation and, thus, to extend the shelf life of the vitamin. In thecase of a flavoring agent, the encapsulation may be carried out to placethe flavoring agent in an easily metered form which will release theflavoring agent at a controllable event, such as the addition of water.

It is generally known to skilled practitioners in the field of flavorencapsulation that current practical commercial processes leading tostable, dry flavors are generally limited to spray drying and extrusionfixation. The former process requires the emulsification orsolubilization of the flavor in a liquid carrier containing theencapsulating solids, followed by drying in a high temperature, highvelocity gas stream and collection as a low bulk density solid.

While spray drying accounts for the majority of commercial encapsulatedmaterials, several limitations of the process are evident. Low molecularweight components of complex or natural flavor mixtures may be lost ordisproportionate during the process. The resultant flavor-carriers areporous and difficult to handle. In addition, deleterious chemicalreactions such as oxidation can result on surfaces exposed during andafter drying. The final product, a dry, free flowing powder, willrelease the encapsulant rapidly upon rehydration whether rapid releaseis desired or not.

U.S. Pat. No. 3,971,852, to Brenner et al., teaches the use of modifiedstarch, gums and other natural hydrocolloids with lower molecular weightpolyhydroxy compounds to yield a glassy cellular matrix withencapsulated oil at a maximum of 80 volume %. This system forms a shellsurrounding the oil flavoring but is limited to lipophilic flavoringagents. Saleeb and Pickup, in U.S. Pat. No. 4,532,145, describe aprocess and composition in which a volatile flavorant is fixed by spraydrying from a carrier solution made up of 10-30% of a low molecularweight component such as a sugar or an edible food acid with the balanceof solids being a maltodextrin carbohydrate in the amount of 70-90%.U.S. Pat. No. 5,124,162, to Boskovic et al., discloses a carrier mixturecomposed of mono- and disaccharides (22-45%), maltodextrins (25-50%),and a high molecular weight carbohydrate such as gum arabic, gum acaciaor chemically modified starch (10-35%) to which flavoring agents areadded and the subsequent solution spray dried to yield a free flowingpowder with a bulk density of 0.50 g/cc.

Several technical issues unmet by these approaches cited are evident.Firstly, thermally sensitive flavors undergo undesirable reactions,including oxidations, rearrangements and hydrolyses. Secondly, volatilecomponents are lost during the atomization and evaporation in the dryer.

A second process route, that of melt encapsulation, has been utilized toadvantage with lipid-based flavors. In this technology a melt isprepared in the form of a high solids carbohydrate syrup, flavoring oilswith emulsifier are added under pressure, agitated, and dispersed, andthe mixture is injected into a chilling, dehydrating solvent bath toobtain fine, rod-like filaments. After the solvent removal, the matrixis reduced in size and, in some cases, coated with anti-caking agentsbefore being packed. Description of the key parameters of this processcan be found in the U.S. Pat. Nos. 2,809,895 and 3,0410,180, to Swisher,U.S. Pat. Nos. 2,856,291 and 2,857,281, to Shultz, U.S. Pat. No.3,704,137, to Beck, and subsequent improvements in the art are detailedin U.S. Pat. No. 3,314,803 for encapsulation of volatiles such asacetaldehyde.

An alternative route to encapsulating flavorings is taught by Sair andSair, in U.S. Pat. No. 4,230,687. In this approach, high molecularweight carriers such as proteins, starches or gums are plasticized byaddition of water in the presence of the encapsulate and subjected to ahigh shear dispersive process. The dispersed matrix plus encapsulate isthen recovered and dried to yield a stable product.

Another alternative process, melt extrusion, can be utilized for flavorfixation and encapsulation. In this process, a melting system, i.e. anextruder, is employed to form the carrier melt in a continuous process.The encapsulate flavor is either admixed or injected into the moltencarbohydrate carrier. Saleeb and Pickup teach, in U.S. Pat. No.4,420,534, use of a matrix composition consisting of 10 to 30 wt % of alow molecular weight component chosen from a series of mono- ordisaccharides, corn syrup solids, or organic acid with the balance ofthe mixture being maltodextrin. The matrix base is dry blended with ananhydrous liquid flavoring component and melted in a single screwextruder to yield a solid matrix characterized as a glass with a glasstransition temperature >40° C.

Levine and Slade, in U.S. Pat. Nos. 5,087,461 and 5,009,900, teach asimilar approach utilizing a composition consisting of a modified foodstarch, maltodextrin, polyol, and mono- and disaccharide components. Thestarch is a chemically modified, water-soluble starch and is used in anamount of 40 to 80% of the total mixture. The balance of the compositionis comprised of 10-40% of maltodextrin, 5 to 20% of corn syrup solids orpolydextrose and 5-20% of mono- or disaccharide. This matrix is made tobalance processing response with glass matrix character.

In the two preceding examples in the '461 and '900 patents, the matrixcomposition was carefully defined to accommodate the processinglimitations of the extruder as well as to generate a stable matrix beingin the glassy state and characterized by a glass transition temperatureof >40° C.

Formation of a matrix in the glass state is of particular value forencapsulation of water-soluble flavorings and extracts. In these cases,the role of water as a plasticizing agent conflicts with this desiredresult, because water in the final product has the effect of loweringthe glass transition temperature (T_(g)) of the glassy matrix. In modelstudies of a number of food carbohydrate systems, the upper limit ofwater content is approximately 7-10 wt. % for lower molecular weightcomponents such as mono- and disaccharides, maltodextrins andcombinations of these agents. At higher water contents, the T_(g) islowered to the extent that the matrix is in the undesirable rubbery orplastic state at room temperature.

In order to insure higher T_(g) 's there are several options available.By limiting the class of encapsulate materials to lipophilic materialssuch as citrus oils, plasticizing moisture may be removed by a boil offprocess as described in U.S. Pat. No. 2,809,895. Alternatively, the useof melt encapsulation as taught in U.S. Pat. No. 4,420,534 limits theflavoring agents to materials with lower vapor pressure which can beadmixed to the premelt composition. In addition, flavorings which are inthe form of aqueous extracts, water, and alcohol-water solutions willresult in a product with a T_(g) much below 25° C. leading to plasticflow and loss of volatiles upon storage.

Similarly, in U.S. Pat. No. 5,009,900, the flavorings are limited tothose with limited volatility and total moisture levels in the finalproduct are less than 11% by weight. Many of the key topnotes and uniqueflavor components of complex flavors have high vapor pressures at roomtemperature and are not easily encapsulated by such a process.

Preparation of a solid in the glass state is dependent upon both matrixcomposition and the process used to generate the encapsulating material.The advantages of retaining the glass form of the matrix is increasedphysical stability of the solid, reduced loss of incorporated volatiles,and reduction of deleterious intermolecular reactions. A detaileddiscussion of the physical chemistry of water-food polymer interactionsas relating to the glassy state and their transition temperatures can befound in H. Levine and L. Slade, "Glass Transitions in Foods", pgs.83-205 in Physical Chemistry of Foods, H. Schwartzberg and R. Hartel,Eds., Marciel Dekker, New York, 1992; and H. Levine and L. Slade, "Wateras a Plasticizer: physico-chemical aspects of low-moisture polymericsystems", pgs. 79-185 in Water Science Reviews, Vol. 3, F. Franks, Ed.,Cambridge University Press, London, 1988, which are incorporated hereinby reference. The role of water as plasticizer with food polymers, aswell as the relationships between molecular composition and dynamics ofinteractions between various components, are discussed in thesereferences.

Thus, there remains a need for encapsulation compositions in which anencapsulate is encapsulated in a matrix which is stable in the glassstate at ambient temperatures. In particular, there remains a need forflavor encapsulation compositions in which a flavoring agent isencapsulated in a matrix which is stable in the glassy state at roomtemperature, i.e., has a T_(g) sufficiently high to prevent caking andplastic flow at ambient temperatures. There also remains a need forflavor encapsulation compositions which have a high T_(g) and areamenable for encapsulating volatile and sensitive flavor components.

SUMMARY OF THE INVENTION

Accordingly, it is one object of the present invention to provide novelencapsulation compositions in which an encapsulate is encapsulated in amatrix which is stable in the glassy state at ambient temperatures.

It is another object of the present invention to provide novel flavorencapsulation compositions in which a flavoring agent is encapsulated ina matrix which is stable in the glassy state at ambient temperatures.

It is another object of the present invention to provide novel flavorencapsulation compositions which are amenable to the encapsulation ofvolatile or sensitive flavor components.

These and other objects, which will become apparent during the followingdetailed description, have been achieved by the inventors' discoverythat it is possible to prepare carbohydrate-based glassy matrices, whichhave a sufficiently high T_(g) to prevent plastic flow and caking atambient temperatures, by interacting one or more carbohydrate foodpolymers with an aqueous plasticizer in the melting zone of an extruderand extruding the resulting mixture.

The inventors have also discovered that a composition comprising:

(A) an encapsulate, encapsulated in:

(B) a glassy matrix, comprising:

(a) 95 to 100 wt. % of a maltodextrin having 5 to 15 dextroseequivalents (D.E.); or

(b) 45 to 65 wt. % of a maltodextrin having 5 to 15 D.E. and 35 to 55wt. % of corn syrup solids having 24 to 42 D.E.; or

(c) 80 to 95 wt. % of a maltodextrin having 5 to 15 D.E., 1 to 15 wt. %of a salt of an organic acid, and 0 to 15 wt. % of an organic acid; or

(d) 25 to 80 wt. % of a maltodextrin having 5 to 15 D.E., 2 to 45 wt. %of a food polymer, and 10 to 30 wt. % of a mono- or disaccharide or cornsyrup solids having 24 to 42 D.E.; or

(e) 45 to 80 wt. % of a maltodextrin having 5 to 15 D.E., 2 to 22 wt. %of a carbohydrate polymer having carboxylate or sulfate side groups, 5to 30 wt. % of corn syrup solids having 24 to 42 D.E., and 0.2 to 2.0wt. % of a soluble calcium salt; or

(f) 30 to 100 wt. % of a modified starch (e.g. sodium octenyl succinatemodified starch), and 0 to 70 wt. % of a mono- or disaccharide; or

(g) 85 to 100 wt. % of a modified starch (e.g. sodium octenyl succinatemodified starch), and 0 to 15 wt. % of a polyhydric alcohol,

are stable in the glassy state, i.e., have a sufficiently high T_(g) toprevent plastic flow and caking at ambient temperature.

The present encapsulation compositions may be prepared by a processcomprising:

(i) mixing (a), (b), (c), (d), (e), (f), or (g) with a liquidplasticizer and an encapsulate in an extruder, to obtain a meltedmatrix; and

(ii) extruding said melted matrix.

In one preferred embodiment, the present compositions are prepared byutilizing as the liquid plasticizer a concentrated or saturated aqueoussolution of the matrix mixture or selected mixture components and theplasticizer is added to the melting zone of an extruder. In anotherpreferred embodiment, a concentrated aqueous solution of calcium saltbeing in the hydrated form is used as the plasticizer for interactionwith calcium reactive polymers.

The encapsulate is continuously added in a liquid phase, following themelting of the carbohydrate matrix, by injection under pressure andmixing before exiting the extruder die.

In another embodiment, the present method employs a venting step of thevolatile plasticizer following the melt to reduce the moisture contentto below 10% moisture in the final product.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 illustrates the effect of milling on the physical state of acitric acid-sodium citrate buffer mixture.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As noted above, the present invention has been made possible, in part,by the inventor's discovery that it is possible to preparecarbohydrate-based glassy matrices, which have a sufficiently high T_(g)such that the glassy matrix is stable at ambient temperatures, with useof aqueous plasticizer. Thus, the inventors have discovered that withuse of aqueous plasticizer it is possible to prepare a maltodextrin- ormodified starch-based glassy matrix which does not undergo plastic flowor caking at ambient temperatures. This discovery is a surprising resultconsidering the well-known, large glass-transition-lowering effect ofwater in carbohydrate systems. Accordingly, before the presentinvention, one skilled in the art would not have expected that a stableglassy carbohydrate- or maltodextrin-based matrix could have beenpractically prepared using an aqueous plasticizer.

In one embodiment, the present invention relates to active agentencapsulation compositions in which (A) an encapsulate is encapsulatedin (B) a glassy matrix comprising:

(a) 95 to 100 wt. % of a maltodextrin having 5-15 D.E.; or

(b) 45 to 65 wt. % of a maltodextrin having 5 to 15 D.E. and 35 to 55wt. % of a corn syrup solid having 24 to 42 D.E.;

(c) 80 to 95 wt. % of a maltodextrin having 5 to 15 D.E., 1 to 15 wt. %of a soluble or meltable salt of an organic acid, and 0 to 15 wt. % ofan organic acid; or

(d) 25 to 80 wt. % of a maltodextrin having 5 to 15 D.E., 2 to 45 wt. %of a food polymer, and 10 to 30 wt. % of a mono- or disaccharide or cornsyrup solids having 24 to 42 D.E.; or (e) 45 to 80 wt. % of amaltodextrin having 5 to 15 D.E., 2 to 22 wt. % of a carbohydratepolymer having carboxylate or sulfate side groups, 5 to 30 wt. % of cornsyrup solids having 24 to 42 D.E., and 0.2 to 2.0 wt. % of a solublecalcium salt; or

(f) 30 to 100 wt. % of a modified starch (e.g. sodium octenyl succinatemodified starch), and 0 to 70 wt. % of a mono- or disaccharide; or

(g) 85 to 100 wt. % of a modified starch (e.g. sodium octenyl succinatemodified starch), and 0 to 15 wt. % of a polyhydric alcohol.

The term encapsulate, as used in the present invention, includes agentssuch as medications, pesticides, preservatives, vitamins, flavoringagents, perfumery chemicals and fragrances, and food colorants bothsynthetic and natural. Suitable medications include antacids,anti-inflammatory substances, coronary vasodilators, cerebralvasodilators, peripheral vasodilators, anti-infectives, psychotopics,antimanics, stimulants, antihistamines, laxatives, decongestants,vitamins, gastrointestinal sedatives, antidiarrheal preparations,antianginal drugs, antiarrhythmics, antihypertensive drugs,vasoconstrictors, migraine treatments, anticoagulants, antithromboticdrugs, analgesics, antipyretics, hypnotics, sedatives, antiemetics,antinauseants, anticonvulsants, neuromuscular drugs, hyper- andhypo-glycaemic agents, thyroid and antithyroid preparations, diuretics,antispasmodics, uterine relaxants, mineral and nutritional additives,antiobesity drugs, anabolic drugs, erythropoietic drugs, antiasthmatics,expectorants, cough suppressants, mucolytics, antiuricemic drugs andother drug substances such as topical analgesics, local anesthetics andthe like.

Suitable pesticides include insecticides, nematocides, fungicides,herbicides, and microbicides. Insecticides, which may be encapsulated inthe present compositions include those disclosed in Kirk-Othmer,Encyclopedia of Chemical Technolocy, 3rd Ed., vol. 13, Wiley, N.Y., pp.413-485 (1981), which is incorporated herein by reference. Suitablenematocides include, e.g., methyl N',N'-dimethyl-N-(methylcarbamoyl)oxy!-1-thiooxamimidate (oxamyl) and those disclosed inKirk-Othmer, Encyclopedia of Chemical Technology, 3rd Ed., vol. 18,Wiley, N.Y., pp. 305-8 (1982), which is incorporated herein byreference. Suitable fungicides include those disclosed in Kirk-Othmer,Encyclopedia of Chemical Technology, 3rd Ed. vol. 11, Wiley, N.Y., pp.490-498 (1980), which is incorporated herein by reference. Suitableherbicides include those disclosed in Kirk-Othmer, Encyclopedia ofChemical Technology, 3rd Ed., vol. 12, Wiley, N.Y., pp. 297-351 (1980),which is incorporated herein by reference. Suitable antibiotics andantimicrobials include those disclosed in Kirk-Othmer, Encyclopedia ofChemical Technology, 4th Ed., vol. 2, Wiley, N.Y., pp. 854-1018 (1992)and vol. 3, pp. 1-346 (1992), both of which are incorporated herein byreference. Suitable vitamins include those disclosed in Kirk-Othmer,Encyclopedia of Chemical Technology, 3rd Ed. vol. 24, Wiley, N.Y., pp.1-277 (1984), which is incorporated herein by reference. Suitable foodadditives, in addition to flavoring agents, include those disclosed inKirk-Othmer, Encyclopedia of Chemical Technology, 3rd Ed., vol. 11,Wiley, N.Y., pp. 146-163 (1980), which is incorporated herein byreference.

The term flavoring agent includes spice oleoresins derived fromallspice, basil, capsicum, cinnamon, cloves, cumin, dill, garlic,marjoram, nutmeg, paprika, black pepper, rosemary and tumeric; essentialoils: anise oil, caraway oil, clove oil, eucalyptus oil, fennel oil,garlic oil, ginger oil, peppermint oil, onion oil, pepper oil, rosemaryoil, spearmint oil; citrus oils: orange oil, lemon oil, bitter orangeoil and tangerine oil; alliaceous flavors: garlic, leek, chive, andonion; botanical extracts: arnica flower extract, chamomile flowerextract, hops extract, and marigold extract; botanical flavor extracts:blackberry, chicory root, cocoa, coffee, kola, licorice root, rose hips,sarsaparilla root, sassafras bark, tamarind and vanilla extracts;protein hydrolysates: hydrolyzed vegetable protein (HVP's), meat proteinhydrolyzates, milk protein hydrolyzates; and compounded flavors bothnatural and artificial including those disclosed in S. Heath, SourceBook of Flavors, Avi Publishing Co., Westport, Conn., 1981, pp. 149-277.Representative flavor compounds are for example: benzaldehyde, diacetyl(2,3-butanedione), vanillin, ethyl vanillin and citral(3,7-dimethyl-2,6-octadienal). The flavoring agent may be in the form ofan oil, aqueous solution, non-aqueous solution or an emulsion. Flavoressences, i.e. the water soluble fraction derived from fruit or citruscan be utilized although at lower levels than the ingredients referencedabove. As will be described more fully below, the present invention isparticularly advantageous when the flavoring agent is itself a volatilecompound or is a mixture comprising a number of volatile compounds withvarying vapor pressures at ambient conditions.

When the encapsulate is lipophilic, the encapsulate is dispersed in theglassy matrix of the final product usually with the aid of an emulsifieradded to the lipophilic phase or in the matrix mixture. In contrast,when the encapsulate is hydrophilic or water-soluble, the final productcontains the encapsulate as a dissolved solute and/or as a dispersedencapsulant.

Although the exact amount of encapsulate encapsulated in the matrix willdepend, in part, on the precise nature of the matrix, the identity ofthe encapsulate, and the anticipated end use of the final composition,the encapsulation compositions of the present invention will typicallycomprise 2.5 to 15 wt. % of encapsulate, based on the total weight ofthe encapsulation composition. Preferably, the present encapsulationcompositions will comprise 7 to 12 wt. % of encapsulate, based on thetotal weight of the composition. It is preferred that the encapsulate isa flavoring agent.

In addition to the foregoing encapsulates, various optional ingredientssuch as are conventionally used in the art, may be employed in thematrix of this invention. For example, colorings, sweeteners,fragrances, diluents, fillers, preservatives, anti-oxidants,stabilizers, lubricants, and the like may be employed herein if desired.

As noted above, the encapsulate is encapsulated in a glassy matrix ofone of (a), (b), (c), (d), (e), (f), or (g). In all of the definitionsof matrices (a), (b), (c), (d), (e), (f) and (g), all wt. % values arebased on the total weight of the glassy matrix (B).

In one embodiment, the glass matrix comprises (a) 95 to 100 wt. % of amaltodextrin having 5-15 D.E. Preferably, in embodiment (a), the glassmatrix comprises 95 to 97 wt. % of a maltodextrin having 5-15 D.E.

The relationship between the glass transition temperature and moisturecontent for a maltodextrin matrix has been described by Y. Roos and M.Karel, J. Food Science, Vol. 56(6), 1676-1681 (1991), which isincorporated herein by reference. T_(g). the glass transitiontemperature, increases with decreasing moisture content or increasingmolecular weight of the maltodextrin. The experimental procedure for theglass formation described by Roos and Karel in this reference is notamenable to commercial application. Also noteworthy is that the systemdescribed in this reference, maltodextrin solids and moisture, does notinclude organic flavor solutes. Incorporation of water-soluble lowmolecular weight compounds contributed by most flavors would act as aplasticizer in such a matrix.

Commercial maltodextrins are usually prepared from hydrolysis of aselected corn starch. The resulting maltodextrin products are obtainedas complex mixtures of carbohydrate oligomers which also contain minoramounts of mono- and disaccharides. Any commercial maltodextrin with adextrose equivalent (D.E.) of 5 to 15 may be suitably utilized. However,maltodextrins with 10 to 15 D.E. are preferred. The term dextroseequivalent (D.E.) as used in the present specification refers to thepercentage of reducing sugars (dry basis) in a product calculated asdextrose. Good results have been achieved using Lodex 10 of AmericanMaize Company (Hammond, Ind.). Other commercial maltodextrin-likematerials obtained from rice, wheat, and tapioca starches as well asagglomerated forms of maltodextrins such as the Penwest Food Product,Soludex, are also suitable.

Although the matrix of embodiment (a) is described as comprising 95 to100 wt. % of a maltodextrin having 5 to 15 D.E., it should be understoodthat such material as commercially supplied contains 4 to 7 wt. % ofmoisture and that this water content is implicit in the term"maltodextrin" as used above. In addition, water is also introduced intothe final matrix by the use of the present aqueous plasticizers.Similarly, many of the starting materials in embodiments (b), (c), (d),(e), (f), and (g) will also contain moisture as commercially supplied,and water will also be introduced into the final matrix composition byuse of the present aqueous plasticizers.

Accordingly, it is to be understood that in all of the definitions forembodiments (a), (b), (c), (d), (e), (f), and (g) of the glassy matrix,the relative amounts of the various components are expressed on thebasis of the relative amounts of each component used as received fromthe commercial supplier. In other words, although the components of theglassy matrices are used as received from the supplier and thus containsome moisture, the relative amounts of the components in the glassymatrices are expressed as if the commercially supplied components werecompletely moisture-free. It should be further understood that, althoughthe final glassy matrix may contain water, the water content is notexpressly stated.

The amount of water permissible in the final glass matrix isfunctionally limited by the desired T_(g) of the glass matrix. Thus, theglass matrix will suitably contain water in an amount less than thatwhich would lower the T_(g) below 35° C. Preferably, the glass matrixwill contain water in an amount less than that which would lower theT_(g) of the matrix below 40° C. Although the exact upper limit on theamount of water will depend on the identity of the component ingredientsof the glassy matrix, typically the amount of water present will be 5 to10 wt. %, based on the total weight of the glassy matrix, preferably 5to 9 wt. %, based on the total weight of the glassy matrix.

When, in embodiment (a), the matrix comprises less than 100 wt. %maltodextrin (water implicit), then the balance of the matrix maycomprise up to 5 wt. % of any component which does not adversely effecteither the matrix or the encapsulate. Lower molecular weightcarbohydrates, such as glucose, sucrose, maltose, and 24 to 42 D.E. cornsyrup solids, yield more easily processed matrices when added asadditional components. Other processing aids in the form of extrusion"slip agents" are food emulsifiers, which can combine the concomitantfunction of processing aid and surfactant, include the distilledmonoglycerides of fatty acids, distilled propylene glycol monoesters offatty acids, distilled succinylated monoglycerides of fatty acids suchas the Myverol product series available from Eastman Chemicals Co.;sorbitan fatty acid esters, polyoxyethylene(s) sorbitan monoesters offatty acids; distilled acetylated monoglycerides of fatty acids,monodiglycerides of fatty acids and fats and oils from food lipidsources. These may be added in amounts of 0.25 to 2.5 wt. %.

When the matrix is (a), the liquid plasticizer may be water.Alternatively, maltodextrin melts can also be facilitated by use of aplasticizing agent prepared as an aqueous maltodextrin solution. Theadvantage of this latter procedure is to insure adequate hydration andrapid dispersion of liquid plasticizer into the dry mixture in anextruder. A maltodextrin solution having any concentration up tosupersaturation can be employed as the liquid plasticizer in thisprocedure. Similarly, water-flavoring agent solutions and water-alcoholflavoring agent mixtures, such as vanilla extracts can bepreconcentrated with solids from the dry maltodextrin base to yield asyrup which may be used as the liquid plasticizer.

When a plasticizing system consisting of a 50% w/w! aqueous solution ofLodex-10 as obtained from the supplier, was employed in an amount of 0.9lb with 16.9 lb of Lodex 10, the resultant matrix obtained had a watercontent of 9.8 wt. % (by Karl Fisher method) and a T_(g) of 44° C.

In embodiment (b), the glassy matrix comprises 45 to 65 wt. % of amaltodextrin having 5 to 15 D.E., preferably 48 to 62 wt. % of amaltodextrin having 5 to 15 D.E., and 35 to 55 wt. % of a corn syrupsolid having 24 to 42 D.E., preferably 38 to 52 wt. % of a corn syrupsolid having 24 to 42 D.E. The same types of maltodextrins utilized inembodiment (a) are suitably used in embodiment (b). Thus, themaltodextrins used in embodiment (b) preferably have 10 to 15 D.E.

When the encapsulate to be encapsulated is pH sensitive, it is preferredthat the glassy matrix comprise (c). Many pure compounds and flavoringssystems are pH sensitive. It is well known that heating of foodcarbohydrate polymers in the amorphous form in the presence of acidic orbasic agents will lead to carmelizaton and result in off-flavordevelopment and color formation. Moreover, the presence of low molecularweight acids can be detrimental to flavors present during the meltencapsulation process.

When the matrix is (c), it comprises 80 to 95 wt. % of a maltodextrinhaving 5 to 15 D.E., 1 to 15 wt. % of a soluble or meltable salt of anorganic acid, and 0 to 15 wt. % of an organic acid, dry basis. Thematrix, in embodiment (b), preferably comprises 80 to 90 wt. % of amaltodextrin having 10 to 15 D.E., 1 to 14 wt. % of a soluble ormeltable salt of an organic acid, and 0 to 13 wt. % of an organic acid,dry basis. The same types of maltodextrins which are suitable for use inembodiment (a) are also suitable for embodiment (c). Further, asdescribed above with reference to embodiment (a), it should beunderstood that the maltodextrin used in embodiment (c) will typicallycontain 5 to 8 wt. % of moisture as received from the commercialsupplier and that moisture will also be introduced into the final matrixby the use of the present aqueous plasticizers.

Suitable organic acids include those such as citric, malic, adipic,cinnamic, fumaric, maleic, succinic, and tartaric acid, and the mono-,di-, or tribasic salts of these acids are suitable organic acid salts.Suitable salts of these acids are the soluble or meltable salts andinclude those salts in which one or more acidic protons are replacedwith a cation such as sodium, potassium, calcium, magnesium, andammonium. Preferred salts include the sodium and potassium salts ofcitric acid.

The buffer is suitably prepared having a ratio of acid to trisodium acidsalt of 10:1 to 1:4, preferably 4:1 to 1:2; or an acid to disodium saltratio of 10:1 to 1:6, preferably 3:1 to 1:3; or an acid to monosodiumacid salt ratio of 10:1 to 1:10, preferably 2:1 to 1:2. Mixed bufferscan be prepared in which the acid and acid salt are from differentacids.

When the acid and/or acid salt exist in a high melting crystalline form,then the addition of moisture may not plasticize or melt the acid-acidsalt rapidly in the mixture with the maltodextrin. Furthermore, additionof excess water, in this case, would result in a lowering of the T_(g)of the resulting matrix to an undesirable level. Accordingly, in suchcases it is preferred to co-mill the acid/acid salt mixture prior tomixing with the maltodextrin. It has been found that co-milling theacid/acid salt mixture generates an amorphous binary solid solution.This binary solid may then be mixed with desired ternary component suchas a maltodextrin and the mixture melt-extruded.

The co-milling of the acid/acid salt mixture may be carried out in anyconventional milling apparatus such as ball mills and centrifugal impactmills. Typically the acid and acid salt are combined in the proportionsto be used in the matrix and milled. A single pass through a Brinkmannlaboratory impact mill fitted with 0.5 mm screen is adequate to convertall the crystalline phases of a citric acid-trisodium citrate mixtureinto the amorphous, non-crystalline state as determined by DSC.

FIG. 1 shows the effect of milling on the physical state of the citricacid-sodium citrate buffer mixture as evidenced by DSC thermal analyses.Curve 1 (-) represents the thermogram of an unprocessed mixture. Twomelt transitions are evidenced corresponding to the melting of the acidand acid salt respectively. Curve 2 (---) represents the identicalmixture after a single pass through a Brinkmann impact mill. Theamorphous character is noted by a change in baseline corresponding tothe 60-100° C. region. The exotherm centered at approximately 120° C.indicates recrystallization of an amorphous component(s). Finally, atthe higher temperature region of the scan, the crystalline phasesundergo a melt transition. This amorphous mixture will ultimately returnto the more stable crystalline state, i.e., samples made as describedabove exhibit only melt transitions after 10 days at ambienttemperature. The benefit in the use of the amorphous acid-acid saltingredient is increased speed and ease of solution into the maltodextrinmelt.

In another embodiment, the matrix is (d), a mixture comprising 25 to 80wt. % of a maltodextrin having 5 to 15 D.E., 2 to 45 wt. % of a foodpolymer, and 10 to 30 wt. % of a mono- or disaccharide or corn syrupsolids having 24 to 42 D.E., dry basis. Preferably in embodiment (d),the matrix comprises 45 to 70 wt. % of a maltodextrin having 10 to 15D.E., 5 to 20 wt. % of a food polymer, and 25 to 30 wt. % of a mono- ordisaccharide or corn syrup solids having 24 to 42 D.E.

Examples of suitable food polymers include methyl cellulose,hydroxypropyl methyl cellulose, high methoxypectin, gum arabic (acacia),locust bean gum, guar gum; the lesser utilized natural gums such as gumghatti, gum tragacanth, gum karaya; proteins such as gelatin orα-casein; microbial gums such as xanthan, or gellan; pregelatinizedstarches in addition to carbohydrate polymers such as inulins,beta-glucans and konjac flour. Methyl cellulose and hydroxypropyl methylcellulose are preferred.

For some of the compounds used as the food polymer in embodiment (d),the molecular weight is essentially controlled by the source and, infact, may not be precisely known. For example, the gums listed above arenot characterized or described by those of skill in the art in terms ofmolecular weight. Instead, such gums are fully characterized byidentification of their source. Thus, e.g., the term "gum arabic" fullyand completely defines a particular composition and no furthercharacterization is required.

In contrast, the molecular weight of a cellulose ether, such as methylcellulose or hydroxypropyl methyl cellulose, is generally expressed interms of the viscosity at 20° C. of an aqueous solution containing 2 wt.% of the cellulose ether. Suitable cellulose ethers for use inembodiment (d) are those having a viscosity of 3 to 100,000 centipoises,preferably 4000 to 15,000 centipoises. Cellulose ethers are alsocharacterized in terms of the degree of hydroxypropoxyl and methoxylsubstitution. The term "methoxy degree of substitution" (MDS) refers tothe average number of methyl ether groups present per anhydroglucoseunit of the cellulose molecule. The term "hydroxypropoxyl molarsubstitution" (HPMS) refers to the average number of moles of propyleneoxide which are reacted with each anhydroglucose unit of the cellulosemolecule. In embodiment (d), the methyl cellulose suitably has a MDS offrom 19 to 31, preferably 27 to 31. The hydroxypropyl methyl cellulosesuitably has a MDS of from 19 to 30, preferably 24 to 30, and a HPMS offrom 4 to 12, preferably 7 to 12.

Gelatin is not usually characterized in terms of molecular weight butinstead is characterized in terms of "Bloom" or jelly strength asmeasured with a Bloom Gelometer. In embodiment (d), suitable gelatinsare those having a Bloom of 50 to 300, preferably 100 to 300. Both TypeA and Type B gelatin may be used.

The same types of maltodextrins described as being suitable forembodiments (a), (b), and (c) are also suitable for embodiment (d).Preferably the maltodextrin has 10 to 15 D.E. in embodiment (d).

Mono- and disaccharides suitable for use in embodiment (d) includeglucose, fructose, galactose, ribose, xylose, sucrose, maltose, lactose,cellobiose, and trehalose; polyols, e.g., glycerin and propylene glycol;as well as corn syrup solids, high fructose corn syrups, high maltosecorn syrups and hydrogenated corn syrups. Preferred are glucose andmaltose. Corn syrup solids having 24 to 42 D.E. are also preferred.

Glass matrices prepared from low molecular weight components such asmonosaccharides, disaccharides, corn syrup solids and maltodextrins arestable at ambient conditions if the glass exhibits a T_(g) of >30° C.However, release of solutes is relatively rapid when placed in aqueousmedia. A common method for controlled release in the pharmaceuticalindustry employs direct compression of tablets prepared with methylcellulose and hydroxypropyl methyl cellulose in various combinationsfrom 98% to less than 26% of modified celluloses. The procedures employdry blending of all components followed by a wet or dry tabletingprocess. These teachings are described in part in the technical brochure"Formulating for Controlled Release with METHOCEL Premium CelluloseEthers" Dow Chemical Company, Midland, Mich., 1987, but are not directlyapplicable to volatile and liquid agents as desired by the foodindustry.

It has now been found that modified cellulose ethers such as methylcellulose Methocel A; Dow Chemical Co.!, hydroxypropyl methyl celluloseMethocel E,F,J,K; Dow Chemical Co.!, when combined with a maltodextrinor maltodextrin-sugar solids base, yield glassy matrices with increasedT_(g), which are suitable for the encapsulation of volatile flavoringsand flavor compounds. In addition, the modified cellulose polymerrehydrates to develop increased viscosity of the matrix and slow thediffusion of the solute agents into the aqueous media, upon hydration inapplication, i.e., from extraneous water in contact with theglass-flavor matrix.

An exemplary series of methyl cellulose/hydroxypropyl methyl cellulosemixtures were prepared and are shown below. The mixtures have thecomposition ranges of:

    ______________________________________    a! Methyl cellulose                 Dow, Methocel A4M!                                  2 to 45 wt. %    b! Maltodextrin                 American Maize, Lodex-10!                                 20 to 80 wt. %    c! Corn syrup solids                 American Maize, Frodex 42!                                 20 to 30 wt. %    ______________________________________

More preferably the composition was made of the components in the range:

    ______________________________________    a! Methyl cellulose                 Dow, Methocel A4M!                                  4 to 25 wt. %    b! Maltodextrin                 American Maize, Lodex-10!                                 25 to 80 wt. %    c! Corn syrup solids                 American Maize, Frodex 42!                                 20 to 30 wt. %    ______________________________________

and the most preferred mixture had a composition of:

    ______________________________________    a! Methyl cellulose                 Dow, Methocel A4M!                                  5 to 20 wt. %    b! Maltodextrin                 American Maize, Lodex-10!                                 45 to 75 wt. %    c! Corn syrup solids                 American Maize, Frodex 42!                                 25 to 30 wt. %    ______________________________________

Encapsulation was tested utilizing an extruder to which moisture wasadded to the original dry mix at the feed port. Simultaneously with theaddition of the water, orange oil containing selected emulsifier, wasinjected into the melt zone of the extruder. The added moisture islimited to addition of no more than 3 to 5 wt. % additional moisture tothe dry mix. Analysis of the encapsulating matrix shows T_(g) 's in therange of 35 to 50° C.

In another embodiment, the matrix comprises (e) 45 to 80 wt. % of amaltodextrin having 5 to 15 D.E., 2 to 22 wt. % of a carbohydratepolymer having carboxylate or sulfate groups, 5 to 30 wt. % of cornsyrup solids having 24 to 42 D.E., and 0.2 to 2.0 wt. % of awater-soluble calcium salt, dry basis. Preferably, matrix (e) comprises40 to 80 wt. % of a maltodextrin having 10 to 15 D.E., 4 to 15 wt. % ofa carbohydrate polymer having carboxylate or sulfate groups, 10 to 25wt. % of corn syrup solids having 24 to 42 D.E., and 0.4 to 1.8 wt. % ofa water-soluble calcium salt, dry basis.

Suitable carbohydrate polymers having carboxylate or sulfate groups arewater-soluble and are represented by sodium carboxymethyl cellulose(CMC), low methoxy pectin(s), sodium alginate, and {kappa} and {iota}carrageenan(s).

The molecular weight of sodium carboxymethyl cellulose is generallyexpressed in terms of viscosity at 25° C. of an aqueous solutioncontaining 1 wt. % of the sodium carboxymethyl cellulose. In embodiment(e), the sodium carboxymethyl cellulose suitably has a viscosity of 50to 8000 centipoises, preferably 2000 to 8000 centipoises. In additionsodium carboxymethyl cellulose may be characterized in terms of thedegree of substitution (DS) of the hydroxyl groups at carbons C-2, C-3,and C-6 of the d-glucose units. When all the hydroxyl groups aresubstituted the cellulose derivative is said to have a DS of 3. Inembodiment (e), the sodium carboxymethyl cellulose suitably has a DS of0.7 to 1.0, preferably 0.7 to 0.9.

Suitable low methoxy pectins are those having a degree of esterificationof 0.2 to 0.5.

Sodium alginate is commercially available from Hercules Company underthe trade name AQUALON® and may be used directly as received. Iotacarrageenan is sold by Sigma Chemical Company under the name CarrageenanType V.

The same types of maltodextrins used in embodiments (a)-(d) may also beused in embodiment (e). Preferably, the maltodextrin has 10 to 15 D.E.in embodiment (e). The corn syrup solid in embodiment (e) preferably has24 to 42 D.E.

Suitable soluble calcium salts include inorganic salts such as CaCl₂, orCaHPO₄ or salts of organic acids such as calcium lactate or calciumacetate. Less preferred is the use of calcium salts of the organic acidsin the crystalline form admixed with the dry components of the matrix.

The solution chemistry of food hydrocolloids containing carboxylategroups such as the polygalacturonide polymer low methoxy pectin,modified celluloses such as CMC (carboxymethyl cellulose), and thesulfate containing {kappa} and {iota}-carrageenan is known. However, ithas now been found that when these polymers become plasticized in thelow moisture environment of a carbohydrate melt, the interaction betweencarboxylate or sulfate side chain groups no longer follows the expectedteachings of the food technology as known from the fully hydratedpolymers in solution. It has now been found that to obtain the desiredresponse of increased effective molecular weight of the cross-linkedpolymer, the calcium ion is preferably in a hydrated form. This resultis achieved by use of concentrated solutions of highly soluble calciumsalts, i.e., calcium lactate and calcium chloride. The largeconcentration of hydrated calcium ion allows limited amounts ofadditional free water to be added as plasticizer. In addition, separatedliquid streams, one of saturated CaCl₂ or calcium lactate and a secondof plasticizing aqueous media, can be metered to optimize the meltextrusion process and yield the largest T_(g) 's consistent with theoperating conditions of the extruder.

Exemplary compositions comprised of calcium sensitive food polymer,based upon low methoxy pectin, were prepared as a dry blend as:

    ______________________________________     a! low methoxy pectin                          2 to 22 wt. %     b! maltodextrin     45 to 80 wt. %     c! corn syrup solids                          5 to 30 wt. %    ______________________________________

A more preferred formulation range is:

    ______________________________________     a! low methoxy pectin                          4 to 15 wt. %     b! maltodextrin     45 to 80 wt. %     c! corn syrup solids                         10 to 30 wt. %    ______________________________________

and an especially preferred range is:

    ______________________________________     a! low methoxy pectin                          5 to 10 wt. %     b! maltodextrin     50 to 75 wt. %     c! corn syrup solids                         15 to 25 wt. %    ______________________________________

The solubility of carbohydrate polymers in concentrated sugar mediavaries widely. For example those gums and hydrocolloids utilized in theconfectionery industry e.g. high methoxy pectin, gum arabic andbacterial gums such as gellan have been found to function well in themelt extrusion process. These polymers have been found to melt underconditions that did not cause interactions of the plasticizing water andlow molecular weight components to generate extremely high viscositymelts.

A series of polymers cited above were tested for melt compatibility withthe maltodextrin-sugar solids-water plasticizing carrier. Of thesetested, the high methoxy pectin and gellan worked most efficaciously inthe melt-extrusion process. The addition of these polymers alsoincreased the glass T_(g).

The following formulations were utilized:

    ______________________________________     a! food polymer        5 to 25 wt. %     b! maltodextrin  5-15 DE!                           40 to 80 wt. %     c! mono- or disaccharide/                           10 to 30 wt. %      or corn syrup solids  24-42 D.E.!    ______________________________________

A more preferred range would be:

    ______________________________________     a! food polymer        5 to 15 wt. %     b! maltodextrin  5-15 DE!                           50 to 70 wt. %     c! mono- or disaccharide/                           10 to 30 wt. %      or corn syrup solids  24-42 D.E.!    ______________________________________

The relative composition is dependent upon the ingredient form of thepolymer. In many cases, such as with high methoxy pectin and gellan, thesupplier will dilute with functional or food inert materials tostandardize the ingredient for normal commercial usage. In those cases,the above compositions are adjusted to account for the additionalingredients.

In the case of gellan, a non-diluted form of the polymer was obtainedfrom the supplier, Kelco. The following formulation would be arepresentative composition:

    ______________________________________     a! gellan (KELCOGEL ®)                             7.0 wt. %     b! maltodextrin (Lodex-10)                            61.5 wt. %     c! corn syrup solids (Frodex-42)                            30.0 wt. %     d! buffer (Citric Acid: NaCitrate -1:2)                             1.5 wt. %    ______________________________________

The dry ingredients `a` through `d` were prepared as a preblendedmixture and processed by melt extrusion with injection of orange oilunder pressure into the matrix melt. The resulting glassy matrixcontaining the encapsulated orange oil had a T_(g) of 45° C.

When the matrix is (f), the maltodextrin is replaced by a modifiedstarch, i.e. the sodium octenyl succinate modified starch. A mixturecomprising 30-100 wt. % of modified starch and the balance 0-70 wt. % ofmono- or disaccharide is utilized. Preferably, in embodiment (f), thematrix comprises 60 to 90 wt. % modified starch and 10 to 40 wt. % mono-or disaccharide. A preferred modified starch is sold under the tradename of CAPSUL® (National Starch Co.) which is characterized as a sodiumoctenyl succinate modified starch. Similar functional ingredients areavailable from American Maize Company as the Amiogum 23 product. Othermodified starches with similar functionality include the National StarchPurity Gum BE, 1773, and 539. Suitable mono- and disaccharides include,e.g., glucose, sucrose, lactose, fructose, and maltose. Preferred areglucose, sucrose, and maltose.

When the matrix is (g), the modified starch is utilized with aplasticizer consisting of polyhydric alcohol or polyhydric alcohol-watermixtures added in a liquid feed to the base. The functional mixture thencomprises 85 to 100 wt. % modified starch and 0 to 15 wt. % polyhydricalcohol. Preferably in embodiment (g) the matrix comprises 85 to 95% wt.% modified starch and 5 to 15 wt. % polyhydric alcohol. The samemodified starches used in embodiment (f) may be used in embodiment (g).Suitable polyhydric alcohols include propylene glycol and glycerin.

The encapsulation compositions of the present invention may be preparedby a process involving: (i) mixing (a), (b), (c), (d), (e), (f), or (g)with a liquid plasticizer and an encapsulate in an extruder, to obtain amelted matrix; and (ii) extruding said melted matrix.

The present process may be carried out in a conventional single screw orco-rotating twin screw extruder. The choice of using a single or twinscrew extruder will depend on a number of factors but mainly on theconveying properties of the matrix and the encapsulate. A single screwextruder is completely dependent on drag flow, while a twin-screwextruder provides some degree of positive pumping action.

In general, whenever a single screw extruder may be used, it may bereplaced with a twin screw extruder. However, there are circumstanceswhen a single screw extruder may not be used and a twin screw extruderis required. Such circumstances include situations when a glassy matrixwith a high T_(g). is being prepared and a low amount of aqueousplasticizer is added. In this case, use of a single screw extruder mayresult in caramelization of the matrix starting materials and cloggingof the single screw extruder.

In the preparation of the present glassy matrices, the dry carbohydrateand any noncarbohydrate components are mixed with an aqueousplasticizer. The carbohydrate and other matrix components are referredas "dry", but, as discussed above, many of these components willactually contain moisture as received from the commercial supplier. Inthe present process, the matrix components may be used as received.

The aqueous plasticizer may be water, an aqueous solution or suspensionof one of the matrix components (e.g, an aqueous solution of amaltodextrin), an aqueous solution or suspension of an active agent, anoil-in-water emulsion, an alcohol-water solution or suspension of anactive agent (e.g., vanilla extract), an aqueous solution or suspensionof an organic acid or salt of an organic acid, or an aqueous solution orsuspension of a calcium salt. When the matrix is (a) or (b), it ispreferred that the plasticizer is an aqueous solution or suspension ofthe maltodextrin. When the matrix is (c), it is preferred that theplasticizer is an aqueous solution or suspension of one or more of (i)the maltodextrin or (ii) the organic acid and/or salt of the organicacid. When the matrix is (d), it is preferred that the plasticizer is anaqueous solution or suspension of one or more of (i) the food polymer,(ii) the maltodextrin, or (iii) the mono- or disaccharide or the cornsyrup solids. When the matrix is (e), it is preferred that theplasticizer is an aqueous solution or suspension of one or more of (i)the maltodextrin, (ii) the corn syrup solids, and (iii) the calcium saltor compatible constituents selected from (i), (ii), and (iii). When thematrix is (f), it is preferred that the plasticizer is an aqueoussolution or suspension of (i) the monosaccharide, (ii) the disaccharide,or (iii) a mixture of mono- and disaccharide. When the matrix is (g), itis preferred that the plasticizer is an aqueous solution of the polyol.

The exact amount of aqueous plasticizer mixed with the dry matrixcomponents will depend, in part, on the amount of moisture present inthe dry matrix components as received from the supplier, theplasticizing effect, if any, of the active agent, and the T_(g) desiredfor the final matrix. Usually the amount of plasticizer to be added isdetermined by first deciding what range of T_(g) is desired and thenexperimentally determining how much aqueous plasticizer can be addedwhile still achieving the desired T_(g). T_(g) (glass transitiontemperature) values were obtained by Differential Scanning Calorimetry(DSC) using a Mettler Thermal Analysis system employing a D-20calorimeter cell and reported as the temperature at the mid-point of theglass transition. In general, an increase in the moisture content of thefinal matrix of any given composition of the present invention will leadto a decrease in the T_(g). of the final matrix. Further, generallyspeaking, decreasing the total amount of water in the starting materialswill decrease the water content of the final composition. By using thesegeneral relationships and the teachings of the present specification oneof skill in the art can easily determine the proper amount ofplasticizer to be added in order to prepare the present glassy matrices.

Thus, e.g., the starting materials will be utilized as received; themelt process is initiated by addition of excess moisture in the form ofan aqueous liquid consisting of pure water or aqueous solute solutioninto the feed port of the extruder. Upon reaching an initial temperatureand material flow equilibration, the aqueous feed is reduced until theresulting exudate matrix is obtained which upon cooling is determined tobe in the glassy state. With experience using specified matrices, theminimum feed rate for the aqueous component can be set initially and theprocess run to yield the glassy matrix immediately.

The present encapsulation compositions are stable at ambienttemperatures and, thus, have a T_(g) of at least 35° C. Preferably, thepresent encapsulation compositions have a T_(g) of at least 40° C. Thus,the glassy matrix of the present compositions will typically contain 3to 10 wt. % of water, preferably 5 to 9 wt. % of water.

As noted above, the dry components of the matrix and the aqueousplasticizer are mixed in the heating zone of an extruder. Thetemperature to which the heating zone is heated will depend on theidentity of the matrix material and the amount of plasticizer added.Typically, the heating zone will be heated to a temperature of 194 to320° F., preferably 230 to 284° F.

After the plasticizer and dry matrix components have been mixed andmelted, the resulting melted matrix is mixed with the active agent. Thismixing is conveniently carried out in a separate extruder zone,downstream of the heating zone. Alternatively, in the case of athermally stable active agent, the active agent may comprise onecomponent of the aqueous plasticizer or otherwise be mixed with theaqueous plasticizer and dry matrix components in the heating zone of theextruder.

The proportion of encapsulate added will generally equal the proportionof encapsulate in the final composition. Thus, typically, the amount ofencapsulate to be added will be determined by the amount of encapsulatedesired in the final composition.

In the case of volatile encapsulates (such as diacetyl), some loss ofencapsulate may occur by volatilization, when the hot melt exits theextruder. In these cases, the amount of encapsulate in the finalcomposition may be controlled by adding excess encapsulate to the meltedmatrix to compensate for the loss due to volatilization.

In some cases, it may be necessary to add an amount of water to the drymatrix components which would ordinarily result in the amount of waterin the final matrix being so great that the final composition has alower T_(g) than desired. Such instances may arise when the drycomponents are slowly hydrated, and the initial water content must behigh to prevent decomposition of the dry matrix components in themelting zone of the extruder. In these cases, the amount of water in thefinal composition may be lowered to the required level by venting themelted matrix. Venting procedures and suitable apparatus are disclosedin U.S. patent application Ser. No. 07/948,437, which is incorporatedherein by reference. In the case of a nonvolatile active agent, theventing may take place either before or after the mixing of theencapsulate with the melted matrix. In the case of a volatile activeagent, the venting is preferably carried out before the mixing of theencapsulate with the melted matrix.

The final extruded composition may be used as extruded, that is, in theform of an extruded rod or filament. Alternatively, the extrudedmaterial may be further processed, preferably after cooling, by, e.g.,grinding, pulverizing, etc. The ground composition may be used as is forthe storage and/or sustained release of the encapsulate or it may bewashed of surface oils in the case of dispersed encapsulate with foodgrade solvents such as ethanol, isopropanol, hexane and the residualsolvent removed by standard processes.

The present encapsulation compositions are particularly useful for theencapsulation and long-term storage of flavoring agents. The presentcompositions permit the long-term storage of sensitive and/or volatileflavors. The compositions may be added directly to food preparations andoffer the added benefit of being easily metered. In addition, the matrixcomponents contribute little to the flavor and/or aroma of a foodprepared from the present compositions.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

EXAMPLES Example 1

A carbohydrate base consisting of a 10 D.E. maltodextrin Lodex-10,American Maize Company! was fed at a rate of 15 lbs/hr into a twin screwextruder. The jacket temperature was set to 250° F. by means of acirculating hot oil heater. Water plasticizer was added to the entryport at a rate of 7 mls/min. The encapsulate, diacetyl Aldrich ChemicalCo.!, was injected into the molten mixture through a jacket port using apiston metering pump at a rate of 12 mls/minute. The exudate composed ofthe diacetyl-maltodextrin melt was then delivered at 200° F. through adischarge nozzle and collected at ambient pressure. Upon passivecooling, the solid, yellow matrix was characterized by differentialscanning calorimetry (DSC) as a glass with a T_(g) of 50° C. The productcontained 4.9 wt. % diacetyl and 8.3 wt. % moisture (by Karl Fisheranalysis). Following storage of the bulk sample at ambient conditionsfor 4 months, the diacetyl content was analyzed at 4.0 wt. % (82%retention).

Example 2

A carbohydrate base consisting of a 10 D.E. maltodextrin Lodex 10,American Maize Company! was fed at a rate of 15 lbs/hr into an extruderas described in Example 1. A fluid plasticizer consisting of a 50% (w/w)aqueous 10 D.E. maltodextrin solution was added to the feed port at arate of 14 ml/min. The extruder was maintained at a jacket temperatureof 250° F. Prechilled diacetyl Aldrich Chemical Co.! was injected intothe molten matrix through an injection port using a piston metering pumpat a rate of approximately 12 mls/minute. The encapsulate mixturecomposed of the diacetyl-maltodextrin melt was delivered through adischarge nozzle and collected at ambient pressure as an expandedmaterial which rapidly collapsed to yield a translucent yellow solid.The resultant solid was characterized by DSC as a glass with a T_(g) of51° C. The matrix contained 4.4 wt. % diacetyl and 7.6 wt. % moisture(by Karl Fisher analysis). Following storage of the bulk sample atambient conditions for 4 months, the diacetyl content was analyzed at4.0 wt. % (90% retention).

Example 3

A buffered base composition was prepared as a dry blend with thefollowing components.

80 wt. % of 10 D.E. Maltodextrin Lodex 10, American Maize Co.!

10 wt. % of Citric Acid Cargill!

10 wt. % of Sodium Citrate Na₃ Citrate.H₂ O, Pfizer!

The base mixture was fed at the rate of 15 lb/hr. into an extruder asdescribed in Example 1. Water is added to the feed port at 3 ml/min.Prechilled diacetyl was injected into the molten mixture through ajacket port in the extruder using a positive displacement pump at a rateof approximately 8 ml/minute. The molten exudate composed of thebuffered diacetyl-maltodextrin melt was then delivered through adischarge nozzle at 227° F. and collected at ambient pressure. Uponcooling, the matrix was characterized by DSC as a glass with a T_(g) of41° C., at a moisture level of 7.3 wt. % (by Karl Fisher analysis). Theencapsulated flavoring was determined to be 3.0 wt % of diacetyl.

The practical utility of buffered melts is best illustrated when acid orbase sensitive agents are encapsulated. In a separate experimental studythe flavoring compound, diacetyl, was encapsulated using the compositionof sample 4 in Table I with the twin screw extruder. The melt wasobtained as a dark brown solid showing the base catalyzed destruction ofthe alpha-dione compound.

                  TABLE I    ______________________________________    Matrix- Buffer pH Responses    Sample    Matrix          Composition                    Wt %    Prepared Mixture pH                                             Melt pH    ______________________________________    1     Lodex-10  90      this     3.97    3.77          Na.sub.3 Citrate                     5      application          Citric Acid                     5    2     Lodex-10  80      U.S. Pat.                                     2.40    2.32          Citric Acid                    20      No. 4,820,534    3     Lodex 10  80      Example 3                                     3.82    3.88          Citric Acid                    10      this          Na.sub.3 Citrate                    10      application    4     Lodex-10  75      this     7.49    7.44          Frodex 42 15      application          Na.sub.3 Citrate                    10    ______________________________________

Example 4

A matrix composition containing a food polymer was prepared with thefollowing components:

61.0 wt. % of 10 D.E. Maltodextrin Lodex 10, American Maize Co.!

30.5 wt. % of 42 D.E. Corn Syrup Solids Frodex-42, American Maize Co.!

7.0 wt. % of Gellan CF KELCOGEL®, Kelco Co.!

0.5 wt. % of Citric Acid Cargill!

1.0 wt. % of Na₃ Citrate.2H₂ O Pfizer!

The mixture was fed into a dual extruder system in which the initialmelt is obtained by feeding 15 lbs/hr of the base mix into the firstextruder with a jacket heated to 300° F. Water is added to the feed portat the rate of 27 mls/min to yield a molten, plastic mass. This melt wasdischarged with venting of moisture as steam at 268° F. into a secondextruder with the jacket temperature at 300° F. A flavor load consistingof 90 parts orange oil Citrus and Allied! in which is dissolved 10 partspolyglycerol ester emulsifier Caprol 3G0, Witco Chemical Co.! wasprepared and injected through a jacket port in the second extruder usinga metering pump at a rate of 10 mls/min. The product collected from thedischarge outlet of the second extruder unit was obtained as a hot,plastic mass which upon cooling set into a hard, fracturable solid. Theresultant solid was characterized by DSC as a glass with a T_(g) of 41°C., at a moisture level of 6.8 wt. % (by Karl Fisher analysis). Theencapsulated flavoring was determined to be 2.9 wt % of citrus oil.

Example 5

A carbohydrate base matrix containing a functional polymer was preparedas a mixture consisting of:

72.5 wt. % 10.D.E. Maltodextrin Lodex-10, American Maize Co.!

20.0 wt. % 42 D.E. Corn Syrup Solids Frodex-42, American Maize Co.!

7.5 wt. % Methyl Cellulose Methocel A4M, Dow Chemical Co.!

The components were dry blended as obtained. The process described inExample 1 was utilized. Water was delivered into the feed/port at 7ml/min., and orange oil Citrus and Allied! was injected at 12 ml/min.The encapsulated orange oil was retained at 8.3 wt. %, and the matrixwas analyzed at 8.9 wt. % moisture (by Karl Fisher Analysis). The solidwas characterized by DSC as a glass with a T_(g) of 40° C.

Example 6

A matrix composition was prepared with the following components:

70.0 wt. % of 10 D.E. Maltodextrin Lodex 10, American Maize Co.!

20.0 wt. % of 42 D.E.Corn Syrup Solids Frodex-42, American Maize Co.!

10.0 wt. % of Low Methoxy Pectin Type LM104AS, Hercules Inc.!

The extruder was set up as described in Example 1 and operated at jackettemperature of 250° F. and a feed rate of 15 lb/hr. However, two liquidfeed lines were placed at the feed orifice. The first delivered water,and the second delivered an aqueous solution of 27% (w/w) calciumlactate. The water feed rate was 1 ml/min., and the calcium solutionfeed rate was set at 4 ml/min. orange oil Citrus and Allied! with addedpolyglycerol ester emulsifier Caprol 3G0, Witco Chemical Co.! at theratio 90:10 (w/w) was prepared and the liquid injected at 28 ml/min.into the fluid melt. The exit temperature of the matrix was 229° F. Uponcooling to ambient conditions, the collected product resulted in a hard,fracturable solid. This solid was characterized by DSC as a glass with aT_(g) of 39° C. The matrix was analyzed at 7.8 wt. % moisture by KarlFisher! and 9.2 wt. % orange oil.

Example 7

A carbohydrate base consisting of 50 wt. % of 10 D.E. maltodextrin Lodex10, American Maize Co.! and 50 wt. % of 42 D.E. corn syrup solids Frodex42, American Maize Co.! was fed at a rate of 15 lbs/hr into an extruderas described in Example 1. Water plasticizer was added to the feed portat a rate of 2.5 mls/min. The encapsulate, a compounded onion flavor,was injected into the molten mixture through a jacket port using ametering pump at the rate of 12 mls/min. The exudate was collected atambient pressure. Upon cooling the solid matrix containing onion flavorwas characterized by DSC as a glass with a T_(g) of 37° C. at 6.6 wt. %moisture (by Karl Fisher analysis).

Example 8

A carbohydrate matrix base is prepared as follows: 10 D.E. Maltodextrin(Soludex 10, Penwest Foods, Co.) is hydrated by the addition withagitation of 5% (wt/wt) distilled water and the system equilibrated toyield a pre-plasticized carbohydrate as a free-flowing material. Abuffering component composed of 12.4 parts citric acid (Pfizer) and 12.1parts trisodium citrate dihydrate (Cargill) was mixed and blended. Themixture was milled in a Brinkmann laboratory impact mill with a singlepass through a 0.5 mm screen to yield a fine, non-crystalline powdercharacterized as amorphous by DSC analyses (see FIG. 1).

The extrusion base is prepared by immediately combining 80 wt. % of themaltodextrin with 20 wt. % of the milled buffer component. The mixtureis then blended with the encapsulate citral (Aldrich Chemical Co.) at alevel of 5.0 wt. % of the total mixture. The flavor-base mixture is meltextruded in a Braebender single screw extruder, fitted with a 1:1compression screw. Heating zones 1, 2, and 3 were set at ambient, 109°C., and 105° C. respectively and run at a screw speed of 20 rpm. Thesolid exudate was characterized by DSC as a glass with a T_(g) of 41° C.and 7.2 wt. % moisture (by Karl Fisher Analyses) and a citral content of2.6 wt. % by volatile oil analysis.

Example 9

A base consisting of CAPSUL®, a modified starch, (National Starch,Bridgewater, N.J.) was fed at a rate of 15 lb/hr into an extruder asdescribed in Example 1. Water was added as a plasticizer at a rate of 10ml/min. The encapsulate, orange oil, and emulsifier at a 4:1 ratio wereinjected into the molten mixture through a jacket port at a rate of 16grams/min. Upon cooling, the exudate formed a hard, dense solid. Theproduct was analyzed to have a volatile oil content of 5.7% by weight.DSC analysis of the product shows a glass transition (T_(g)) of 49° C.

Example 10

A mixture of 90 wt. % CAPSUL® modified starch (National Starch,Bridgewater, N.J.) and 10 wt. % Amerfond fondant sugar (Amstar, NY,N.Y.) was fed at a rate of 15 lb/hr into an extruder as described inExample 1. Water was added as a plasticizer at a rate of 10 ml/min. Theencapsulate, orange oil, and emulsifier at a 9:1 ratio were injectedinto the molten mixture through a jacket port at a rate of 15 grams/min.Upon cooling, the exudate formed a hard, dense solid. The product wasanalyzed to have a volatile oil content of 8.3% by weight and a moisturecontent of 5.2%. DSC analysis of the product showed a glass transition(T_(g)) of 44° C.

Example 11

A modified starch base of CAPSUL® (National Starch, Bridgewater, N.J.)was fed at a rate of 15 lb/hr into an extruder as described inExample 1. A 1:1 mixture of water:propylene glycol was added as aplasticizer at a rate of 16 ml/min. The encapsulate, orange oil, andemulsifier at a 9:1 ratio were injected into the molten mixture througha jacket port at a rate of 14 grams/min. Upon cooling, the exudate, bothwith and without encapsulate, formed a hard, dense solid.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. An encapsulation composition, comprising:(A) anencapsulate encapsulated in:(B) a glassy matrix consisting essentiallyof 85 to 95 wt. % of a modified starch and 5 to 15 wt. % of a polyhydricalcohol,wherein said polyhydric alcohol is selected from the groupconsisting of propylene glycol and glycerin.
 2. The composition of claim1, having a glass transition temperature of ≧35° C.
 3. The compositionof claim 1, having a glass transition temperature of ≧40° C.
 4. Thecomposition of claim 1, wherein said encapsulate is selected from thegroup consisting of medications, pesticides, vitamins, preservatives,and flavoring agents.
 5. The composition of claim 4, wherein saidencapsulate is a flavoring agent.
 6. The composition of claim 5, whereinsaid flavoring agent is selected from the group consisting of naturalextracts, oleoresins, essential oils, protein hydrolysates, aqueousreaction flavors, and compounded flavors.
 7. An encapsulationcomposition, comprising:(A) an encapsulate encapsulated in:(B) a glassymatrix of matrix components consisting essentially of 85 to 95 wt. % ofa modified starch and 5 to 15 wt. % of a polyhydric alcohol,wherein saidpolyhydric alcohol is selected from the group consisting of propyleneglycol and glycerin and wherein said composition is prepared by aprocess comprising:(i) mixing (a) said modified starch; (b) a componentselected from the group consisting of said polyhydric alcohol andmixtures of said polyhydric alcohol with water; and (c) an encapsulatein an extruder to obtain a melted matrix; and (ii) extruding said meltedmatrix.
 8. The composition of claim 7, having a glass transitiontemperature of ≧35° C.
 9. The composition of claim 7, having a glasstransition temperature of ≧40° C.
 10. The composition of claim 7,wherein said encapsulate is selected from the group consisting ofmedications, pesticides, vitamins, preservatives, and flavoring agents.11. The composition of claim 10, wherein said encapsulate is a flavoringagent.
 12. The composition of claim 11, wherein said flavoring agent isselected from the group consisting of natural extracts, oleoresins,essential oils, protein hydrolysates, aqueous reaction flavors, andcompounded flavors.
 13. The composition of claim 1, wherein said glassymatrix consist of 85 to 95 wt. % of said modified starch and 5 to 15 wt.% of said polyhydric alcohol.
 14. The composition of claim 13, having aglass transition temperature of ≧35° C.
 15. The composition of claim 13,having a glass transition temperature of ≧40° C.
 16. The composition ofclaim 13, wherein said encapsulate is selected from the group consistingof medications, pesticides, vitamins, preservatives, and flavoringagents.
 17. The composition of claim 16, wherein said encapsulate is aflavoring agent.
 18. The composition of claim 17, wherein said flavoringagent is selected from the group consisting of natural extracts,oleoresins, essential oils, protein hydrolysates, aqueous reactionflavors, and compound flavors.
 19. The composition of claim 7, whereinsaid matrix components consist of 85 to 95 wt. % of said modified starchand 5 to 15 wt. % of said polyhydric alcohol.
 20. The composition ofclaim 19, having a glass transition temperature of ≧35° C.
 21. Thecomposition of claim 19, having a glass transition temperature of ≧40°C.
 22. The composition of claim 19, wherein said encapsulate is selectedfrom the group consisting of medications, pesticides, vitamins,preservatives, and flavoring agents.
 23. The composition of claim 22,wherein said encapsulate is a flavoring agent.
 24. The composition ofclaim 23, wherein said flavoring agent is selected from the groupconsisting of natural extracts, oleoresins, essential oils, proteinhydrolysates, aqueous reaction flavors, and compound flavors.
 25. Thecomposition of claim 1, wherein said modified starch is sodium octenylsuccinate modified starch.
 26. The composition of claim 7, wherein saidmodified starch is sodium octenyl succinate modified starch.
 27. Thecomposition of claim 18, wherein said modified starch is sodium octenylsuccinate modified starch.
 28. The composition of claim 19, wherein saidmodified starch is sodium octenyl succinate modified starch.